Two stroke cycle internal combustion engine



Sept. 12, 1967 A. E. BROWN 3,340,857

' TWO STROKE CYCLE INTERNAL COMBUSTION ENGINE 7 Filed Oct. 19, 1965 aSheets-Sheet 1 LUBE on."

Sept. 12, 1967 A. E. BROWN 3,340,857

WO STROKE CYCLE INTERNAL COMBUSTION ENGINE Filed Oct. 19, 1965 I aSheets-Sheet :2

- FIGJI Sept. 12, 1967 A. E. BROWN 3,340,857

I TWO STROKE CYCLE INTERNAL COMBUSTION ENGINE Filed Oct. 19, 1965 3Sheets-Sheet 5 United I States Patent 3,340,857 TWO STROKE CYCLEINTERNAL COMBUSTION ENGINE Arthur E. Brown, 117 E. th St., Corning, N.Y.14830 Filed Oct. 19, 1965, Ser. No. 497,722 9 Claims. (Cl. 123-61)ABSTRACT OF THE DISCLOSURE A reciprocating double acting stepped pistonuncovers inlet ports and exhaust ports at each end of its stroke toobtain uniflow scavenging operations. The engine employs a cross head,but the ordinary piston rod and stuffing box have been eliminated. Acocktail shaker cooling arrangement is employed in a double actingpiston.

gine shown in this present application would have improved fuel economy,reduced maintenance, and longer operating life (but increased initialcost, size, and weight) compared to the engine shown in the co-pendingappli cation. Both engines have their field of application.

General advantages of this engine The engine described herein has thefollowing group of advantages (1 to 8) over conventional engines now ingeneral use. These eight advantages indicate powerful reasons for makingprogress on this engine and for attacking the problems associated withit.

(1) The engine has two power strokes per rotation of each crank andconnecting rod. This permits the engine to have fewer cylinders for agiven power output and/or smoother running.

(2) The engine has uniflow type scavenging (instead of cross flow orloop scavenging) and this secures a better flow pattern with less eddycurrents, less mixing with exhaust gas, and less short circuiting of thescavenge air.

(3) Not required are power poppet valves, power cams, power cam shafts,power rocker arms, or power push rods.

(4) The wrist pin bearing has bi-directional loading and this permitsthis bearing to be lubricated by the very reliable squeeze film process.In a single acting two stroke cycle engine, the load on the wrist pin isgenerally non reversing.

(5') The peak bearing loads are lower because the reciprocating inertiaforce is cushioned at each end of each stroke by a gas pressure force.

(6) The exhaust ports can be made shorter in height because they extendaround the full periphery of the cylinder instead of part way around asin a cross or loop scavenged engine. Thus the working stroke is longerand B.M.E.P. higher.

(7) The engine is double acting, yet no stuffing box is required.

(8) Because of advantages 1 to 7 above, the engine is more compact,lighter in weight, lower in initial cost, and lower in maintenance whencompared with conventional engines now in general use.

Specific objects and advantages of this invention regard, the workingpiston has no con rod side thrust imposed on it since this is borne bythe crosshead 6. The absence of con rod side thrust on the workingpiston reduces its lubrication requirements with a saving of wear andlube oil.

An advantage is that the con rod is not located within the front valvepiston 14 and therefore the diameter of piston 14 is determinedprimarily by the requirement to secure adequate flow area for the inletports 18. This permits the diameters of the valve pistons 14 and 15 tobe reduced with a consequent reduction in the diameter of the workingpiston'13 for a given displacement of the engine. This in turn securestwo advantages: (1) there is less surface area exposed to combustion fora given displacement and (2) there is a smaller circumference to sealfor a given displacement.

The valve pistons 14 and 15 must be sealed to prevent leakage of gas. Anobject of this invention is to employ expanding type seal rings 26 onthe valve pistons instead of using non reciprocating contracting typeseal rings in the valve cylinders. The advantages of this are explainedin subsequent paragraphs (a) to ((1).

Another object is to provide means for imparting a rotational motion orswirl velocity to the air inside the chambers so as to improvescavenging, fuel-air mixing, and combustion.

Another advantage is that the engine is less subject to thermaldistortion. The cylinders are concentric about their axes and so are thepistons which are devoid of wrist pin bosses or holes. Also, the gasflow and the combustion process is concentric about the cylinder axis.Therefore, the thermal expansion of these components will be concentricso as to avoid out of round distortion. Less distortion may secure lessblow by, less oil consumption, and less chance of seizure. The above isin contradiction to non concentric engines such as loop scavengedengines in which air cooled inlet ports and hot exhaust ports arelocated on opposite sides of the cylinder.

Another object is to provide a simple effective method for internallycooling the working piston 13 and its two valve pistons 14 and 15.

Another object is to make the piston assembly a one piece casting whichis easy to cast. The interior of the piston assembly is liquid cooled,yet there is no need to form a tortuous path for the flow of liquidcoolant. The ends of the casting are open for core support. Thesefeatures simplify the casting job.

Another object is to prevent (as much as practicable) the inletscavenging air from being heated prior to its entrance into the workingchambers 23 and 24. This will increase power output, reduce detonation,and probably secure a slight improvement in fuel economy.

Another object is to secure low flow resistance for the flow ofscavenging air on its way to the front inlet ports 18. Low flowresistance aids the scavenging process and reduces scavenge pump powerconsumption.

Another object isto provide an engine which is double acting and whichis relatively compact in overall height even though it employs acrosshead and .a crosshead guide.

Another object is to couple the piston assembly to the crosshead 6 insuch a manner that the cast piston assembly is always locatedprincipally in compression. Thus undesirable tension loads and stressconcentrations in these cast parts are eliminated or reduced to aminimum.

Another object is to provide an engine in which each working cylinder isdouble acting and has only a single exhaust connection. This reduces theamount of exhaust manifolding required and simplifies the engine ingeneral.

Another object is to provide an engine which is double acting, twostroke cycle, and also V type. This permits the engine to be remarkablypowerful for a given overall size. The V arrangement permits somecomponents to perform double duty hence a saving in cost and weight. Theinlet manifolding is simplified. The single exhaust manifold 67 servestwo banks of double acting cylinders and this results in a very simpleexhaust system for such a powderful engine.

Another object is to let the frame top 4 serve a twofold purpose; i.e.(1) it serves as a frame stop and (2) it serves as a crosshead guide.This simplifies construction and reduces cost.

Another object is to incorporate an inlet air manifold 38 in the frametop and thereby save the cost of a separate manifold and improve theappearance of the engine.

Another object is to let the flanged and bolted joint 41 serve a doublepurpose as will subsequently be explained.

Brief description of the drawings FIG. I is a sectional view (takenperpendicular to the crankshaft) of a V engine. Some of the engine partson the right hand side of the drawing have been omitted because of lackof space on the sheet. A separate scavenge pump is shown schematicallyat 36 with arrowed lines 37, 65, and 66, indicating conduit connectionsto 3 separate air manifolds.

FIG. II is a larger scale section view of the mid-portion of the engineshown in FIG. I. The View is taken through the axis of the wrist pin 7in a plane 90 degrees to that of FIG. I.

FIG. III is a larger scale section view of the top portion of the engineshown in FIG. I. The view is taken in the same plane as FIG. II.

FIG. IV is a partial section view of the sleeve 28 and the view is takenthrough the inlet ports 18.

FIG. V is an elevation view of the swirl vane assembly 31.

General description and operation Throughout the description and claims,the front of the engine is defined as being nearer the crankshaft thanthe back.

A crankshaft 1 having multiple crankpins 2 is journaled in the mainframe or crankcase 3. The frame top structure 4 is bolted rigidly to themain frame and is provided with cylindrical bores 5 which serve ascrosshead guides. The crossheads 6 reciprocate in the bores 5 and areconnected to the crankpin by means of the wrist pins 7 and connectingrods 8. The working cylinder 9, front cylinder head 10, and a backcylinder head 11 are all mounted to the frame top with a set of longsteel tension rods 12. The double acting Working piston 13, front valvepiston 14, and back valve piston form a reciprocating piston assembly orunit. The valve pistons reciprocate in bores in their respectivecylinder heads. The piston assembly is fastened to the crosshead bymeans of the hollow steel rod The cylinder and heads have liquid coolantpassages 21. The two combustion chambers and 32 are each provided withat least one fuel gas valve 34 and spark plug 35. The words LUBE OIL areshown in FIG. I to indicate a means for lubricating the crankshaft,connecting rods, and crossheads and to illustrate the presence of oilspray inside the crankcase. The exhaust manifold 67 serves two banks ofdouble acting cylinders.

When near top dead center stroke position, the working piston 13uncovers the exhaust ports 22 and the front valve piston 14 uncovers thefront inlet ports 18 so as to obtain a uniflow type scavenging operationof the front working chamber 23. When the pistons are near bottom deadcenter, scavenging air is supplied through the back inlet ports 19 andthe back working chamber 24 is uniflow scavenged exhausting through thesame ports.

Discussion of valve piston seal rings In order for the engine to besuccessful, it is necessary to provide seal rings for the valve pistons14 and 15. It is advantageous that expanding rings 26 be placed on thevalve pistons and reciprocate therewith instead of employingnonreciprocating contracting rings mounted in the cylinder head. This isexplained in the following paragraphs (a) to (d):

(a) At the time of peak pressure and temperature in the back combustionchamber 25, the seal ring 26 (FIG. III) is shielded by distance B. Inorder for the hot combustion gases to reach ring 26, the gas must traveldistance B in the narrow dead end clearance space 27 between sleeve 17and piston 15. The gases will be substantially reduced in temperatureupon reaching the ring 26 due to the long narrow path B and the coolingeffect of the water cooled head 11 and oil cooled piston 15. Ifcontracting rings were located in the head, they would not have thebenefit of the distance B effect described above and instead would bealways directly adjacent the hot combustion chamber 25.

(b) An external ring groove in piston 15 is much easier to machine andinspect than would be an internal ring groove inside the head 11.

(c) A one piece contracting ring would be difiicult to snap into aninternal ring groove unless the groove were formed of separable pieces.(Too complex.)

(d) It is not necessary to make the piston 15 of a wear resistingmaterial as the seal ring 26 rides with the piston and not against it.

The sleeve 28 projects into the front combustion chamber 32 and thefront inlet ports 18 pass through its wall. The sleeve 28 and the linerportion 16 are the same piece of metal. The purpose of the sleeve 28 isto retain the seal rings 26 so that they do not snap out of theirgrooves. The sleeve-liner 16 has a further function which is describedin the discussion of the crosshead.

Discussion of scavenge air supply system- An object is to prevent (asmuch as practicable) the inlet scavenging air from being heated prior toits entrance into the Working chambers so as to increase the poweroutput and reduce detonation. Therefore, the inlet air is not conductedthrough the center of the piston assembly but is instead introduced ateach end. Concurrently, the pistons are internally cooled by means ofliquid coolant instead of being cooled with the scavenging air.

Referring to FIG. I, scavenge air (from any suitable scavenge pump 36)is conducted 37 to the manifold passage 38 cast in the frame top 4. Thefront head 10 has an off center passage 39 for the purpose of conductingthe inlet air to the back end of the bore 5. The air makes a degree turnat 29 (FIG. II) around the front end of sleeve 16, flows past the swirlvanes 30, and then flows through the front inlet ports 18. Air for theback working chamber 24 is supplied from a separate manifold 40.

The bolted joint 41 serves a double purpose; i.e. (1) It fastens thefront head 10 to the frame top 4 and (2) It conducts inlet air at 39 soas to save a separate bolted connection.

Swirl vanes 30 and 31 are mounted on the piston rod upstream from eachset of inlet ports 18 and 19. The vanes have a spiral contour andthereby impart a swirl velocity to the inlet air prior to passage of theair through the inlet ports. An additional aid in obtaining swirl is toalso slope the inlet ports as shown in FIG. IV.

Internal cooling of pistons cates the wrist pin bearing 42; passesthrough holes 43;

passes along the interior of the wrist pin 7; and then passes throughholes 44, 45, and 46 to the inside of the tube 47 which is locatedinside the hollow steel piston rod 20. The oil then flows to the end ofthe tube (FIG. III) and then flows through radial holes 48 to the hollowinterior 49 of the back valve piston. Oil is allowed to partially fillthe hollow spaces 49, 50, and 51 inside the piston assembly.Reciprocating piston motion and inertia of the oil causes the oil to bethrown back and forth inside the hollow interior thus cooling thepistons. As the pistons approach bottom dead center stroke position, theoil is thrown into the front section 51 (FIG. II) where a static oilpressure is momentarily built up due to the acceleration and the heightof the oil column inside the section 51. This momentary static pressureforces oil through drilled holes 52 into the hollow steel rod 20 wherethe oil then empties down into the frame 3. Near top dead center asimilar action occurs in which the oil flows through holes 53 (FIG. III)into the hollow steel rod 20 and this oil then empties into the frame onthe next downstroke. The rate of oil flow up the con rod and into thepiston assembly can be set approximately constant according to the sizeof the holes 44, 45, and 46 and the supply pressure. When the hollowspace 49, 50 and 51 begins to fill with more oil, the cyclic oilpressure increases due to higher columns of oil inside the pistons. Moreoil pressure causes the oil to drain faster through the holes 52 and 53.It is thus seen that the system is self regulating. That is, the pistonsneither become too full of oil nor do they become starved for coolingoil. There is always a proportion of oil and air inside the pistonassembly. Air alternately re-enters the hollow space 49, 50, and 51 alsothrough the holes'52 and 53.

The center baflle 54 causes oil to splash against the inside walls ofthe working piston 13 (cooling same) and also prevents the oil frombeing thrown from one end of the piston assembly clear to the other endwith a consequent oil hammer effect.

This particular type of oil cooling system for the piston assembly hasseveral advantages which are: (1) The oil is well distributed to allparts of the assembly, (2) The heat transfer rate is greatly improveddue to the violent shaking action, and (3) It is not necessary to guidethe oil along a tortuous path with many small passages in order toassure good distribution of the coolant. Therefore the piston assemblycan be a simple one piece casting.

Discussion of pistons and piston rod The working piston 13 and the twovalve pistons 14 and 15 are cast as an integral unit for rigidity,alignment, and reduced cost. With cocktail shaker type cooling, theinterior of the piston assembly need not be complex in shape and thisaids the casting job. The hollow interior of the casting is open at bothends for core support when pouring the casting. The open ends are closed(at assembly) by the piston rod 20 and disc 55 which clamp the castingtightly in compression. The working piston 13 has a series of radialribs 68, cast inside of it. When a power stroke occurs in the frontcombustion chamber 23, there is a gas pressure force against the frontface 57 of the working piston. This force is transmitted as acompression load through the ribs 68 to the back valve piston 15. Theback valve piston in turn is loaded in compression and transmits theforce to the disc 55 and steel rod 20. The steel rod is then loaded intension as it pulls on the crosshead 6. When a power stroke occurs inthe back combustion chamber 24, the cast piston assembly is still loadedin compression in a similar manner. It is thus seen that by coupling thepiston assembly to the crosshead as shown (clamped at both ends with asteel rod) the casting is subjected essentially to compression loadingand undesirable tensile stresses are avoided. It is well know that mostcast irons are weak in tension but very strong in compression.

The construction shown has the further advantage that stressconcentration at the corner juncture 56 is avoided.

If the front valve piston 14 were attached directly to the crosshead 6(instead of using the piston rod construction shown) then the frontvalve piston 14 would be loaded alternately in tension and compression.The tension load would have to be transmitted around the corner 56 (tothe face 57 of the working piston) causing an undesirable stressconcentration at the corner 56.

It is desirable that the scavenging air have a free unrestricted -flowpath so as to prevent air pressure drops. Referring to FIG. II, thepiston rod 20 does not interfere with the flow of scavenge air (on itsway to the front inlet ports 18) since there is a large annular flowpath 58 between the sleeve 16 and the piston rod 20. The rod is curvedat 59 to give a streamlining effect for the flow of scavenge air.

In summary then, the piston rod 20 secures the following functions andadvantages: (1) It couples the piston assembly to the crosshead withminimum tensile stresses and stress concentrations in the cast pistonassembly, (2) The rod permits unrestricted flow for the scavenge air onits way to the front inlet ports 18, (3) The rod is hollow and serves asa means for securing a special cooling system for the pistons as wasdescribed, and (4) The rod serves as a means of support for the swirlvanes 30 and 31.

Discussion of crosshead An object is to make the engine as compact aspracticable even though it employs a crosshead and crosshead guide.Therefore, the back edge of the crosshead 6 is made to overlap the frontend of the sleeve liner 16 by distance A (FIGS. I and II). Also thethreaded boss 60 and nut 61 are permitted to project inside thesleeveliner 16 when at top dead center. The crosshead is provided with acircular groove 29 which as shown is a smooth semitoroidal shapedcontour. This permits smooth unrestricted flow of the scavenge airaround the front end of the sleeve-liner 16. The crosshead hassufficient length C (FIG. II) so as to resist cocking and give goodriding in the bore 5. Also, an adequate connection for the rod 20 isprovided. It is thus seen that the above desirable features areincorporated in the crosshead shown and at the same time the engine isrelatively compact due to the overlap effect A.

The crosshead may be provided with one or more seal rings 62 for thepurpose of retaining oil in the crankcase and also to prevent thepassage or leakage of scavenge air into the crankcase.

Frame top and crosshead guide In'large engines, it is common practice tomake the frame in two pieces which are generally called the main frame(or bed plate) and the frame top. The two pieces are generally boltedtogether at a joint located above the axis of the crankshaft. This makesa rigid construction, permits easy machining of bearing pedestals, andpermits the heavy crankshaft to be installed from the top without havingto turn the main frame over. A feature of this invention is that theframe top 4 also serves as a crosshead guide and thereby saves the needof extra parts. A third function of the frame top is the cast inmanifold passage 38 for conducting and distributing scavenge air tomultiple cylinders. This reduces cost and improves the appearance of theengine.

While the preferred embodiments of the invention have been described, itwill be understood that the invention is not limited thereto since itmay be otherwise embodied within the scope of the following claims.

What is claimed is:

. 1. In a double acting two stroke cycle internal combustion engine, thecombination of a crankcase, a crosshead guide fastened to saidcrankcase, a working cylinder, a front cylinder head and a back cylinderhead fastened to said working cylinder, said cylinder heads havingreduced diameter bores therein, said working cylinder and said cylinderheads being fastened to said crosshead guide, a crankshaft rotatablymounted in said crankcase, a crosshead reciprocable in said crossheadguide, a connecting rod interconnecting said crosshead and saidcrankshaft for respective reciprocating and rotary motion, a doubleacting working piston reciprocable in said working cylinder, a frontvalve piston and a back valve piston, each valve piston being attachedto said working piston so as to form a reciprocating piston assembly,said valve pistons being reciprocable in the bores of their respectivecylinder heads, a scavenge pump for supplying scavenge air, each valvepiston being adapted to admit scavenge air into the interior of saidworking cylinder, said working cylinder having exhaust ports located inits wall, said working piston being adapted to control said exhaustports, said piston assembly being connected to said crosshead forreciprocative motion, said piston assembly having a hollow interior,means for supplying and conducting oil to and from the hollow interiorof said piston assembly so as to internally cool the piston assembly,said means for conducting oil from the hollow piston assembly interiorincluding means for maintaining a portion of air within the holloyvinterior of said piston assembly so as to obtain a shaking actionserving to provide good circulation and distribution of the oil insidethe piston assembly, and means for regulating the volume of oil inproportion to the Volume of air inside the hollow piston assembly.

2. The combination recited in claim 1 wherein the said means forregulating the volume of oil in proportion to the volume of air insidethe hollow piston assembly is accomplished as follows: (a) Thereciprocating motion of the piston assembly and the effect of inertiacauses the oil inside the piston assembly to be thrown back and forthfrom one end of the hollow piston assembly to the other, (b) As thepiston assembly approaches one end of its reciprocative stroke, inertiacauses the oil to be thrown momentarily to one end of the hollow pistonassembly, (c) A column of oil is momentarily collected in one end of thehollow piston assembly, (d) The acceleration of the piston assemblycauses the oil to momentarily build up a static oil pressure which is inproportion to the height of said oil column, (e) Said static pressureforces oil out of the piston assembly through said means for conductingoil from the interior of said hollow piston assembly, (f) An increase inoil volume causes a higher oil column, hence a higher static oilpressure, hence faster drainage of the oil through said hole, (g) areduction in oil volume causes a lower oil column, hence a lower staticoil pressure, hence slower drainage of the oil, (h) thus the system isself regulating.

3. The combination recited in claim 1 wherein a baifie wall is locatedinside said working piston, said baffie wall serving to cause the oilinside the piston assembly to splash against the inside walls of thehollow working piston and thereby more effectively cool same, saidbaffle wall also serving to prevent an oil hammer effect due to back andforth motion of the oil inside the reciprocating piston assembly.

4. In a double acting two stroke cycle internal combustion engine, thecombination of a crankcase, a crosshead guide fastened to saidcrankcase, a working cylinder fastened to said crosshead guide, a frontcylinder head and a back cylinder head fastened to said workingcylinder, said front cylinder head having a cylindrical bore therein,said crosshead guide having a cylindrical bore therein, a crossheadreciprocable in the bore of said crosshead guide, a crankshaft rotatablymounted in said crankcase, a connecting rod interconnecting saidcrosshead and said crankshaft for respective reciprocating and rotarymotion, a double acting working piston reciprocable in said workingcylinder, a valve piston reciprocable in said bore in the front cylinderhead, said valve piston being smaller in diameter than said workingpiston, said valve piston being smaller in diameter than said crosshead,said valve piston being fastened to said working piston so as to form areciprocating piston assembly, said piston assembly being connected forreciprocative motion to said crosshead, said working cylinder havingwithin it a front working chamber and a back working chamber, a separatescavenge pump for supplying scavenge air, said valve piston beingadapted to admit scavenge air into said front working chamber, saidworking cylinder having exhaust ports controlled by said working piston,said front working chamber having a uniflow type scavenging operationexhausting through said exhaust ports, means for porting and scavengingsaid back working chamber, said crosshead having a circular crosssection, a seal ring adapted to serve as a sliding seal between saidcrosshead and said bore in the crosshead guide, means for supplying lubeoil to said crankshaft and connecting rod, said crosshead and seal ringserving to prevent the escape of said lube oil from the interior of thecrankcase, passage and conduit means for conducting scavenge air fromsaid scavenge pump to said bore in the front cylinder head, the bore insaid front cylinder head serving to conduct the scavenge air to theinterior of said front working chamber, and said crosshead and seal ringserving to prevent passage of scavenge air through the bore of saidcrosshead guide into the interior of said crankcase.

5. In a double acting two stroke cycle internal combustion engine, thecombination of a crankcase, a crosshead guide fastened to saidcrankcase, a working cylinder, at front cylinder head and a backcylinder head fastened to said working cylinder, said working cylinderand said cylinder heads being fastened to said crosshead guide, acrosshead reciprocable in said crosshead guide, a crankshaft rotatablymounted in said crankcase, a connecting rod for converting thereciprocating motion of said crosshead to the rotary motion of saidcrankshaft, a double acting working piston reciprocable in said workingcylinder, a valve piston smaller in diameter than said working piston,said valve piston being attached to said working piston so as to form areciprocating piston assembly, said front cylinder head having a boretherein smaller in diameter than said working cylinder, said valvepiston being reciprocable in said bore in the front cylinder head, saidworking cylinder having within it a front working chamber and a backworking chamber, a separate scavenge pump for supplying scavenge air,said valve piston being adapted to admit scavenge air into said frontworking chamber, said working cylinder having exhaust ports located inits wall, said working piston being adapted to control said exhaustports, said front Working chamber having a uniflow type scavengingoperation exhausting through said exhaust ports, means for porting andscavenging said back working chamber, a piston rod interconnecting saidpiston assembly and said crosshead for reciprocative motion, said pistonrod being smaller in cross section than the diameter of said valvepiston, said piston rod passing inside said bore in the front cylinderhead, a sleeve fastened to said front cylinder head, said sleeveprojecting from the front end of said front cylinder head towards saidcrosshead, said valve piston being reciprocable within said sleeve, saidvalve piston being smaller in diameter than said crosshead, saidcrosshead having a groove formed in its back end, said groove serving asa clearance space for the front end of said sleeve when the crosshead isat the top dead center position of its reciprocative stroke, the backedge of said crosshead overlapping the front end of said sleeve when thecrosshead is at the top dead center position of its reciprocativestroke, means for conducting scavenge air from said scavenge pump to theback interior of said crosshead guide, said groove in the crossheadbeing adapted to conduct the flow of scavenge air around the front endof said sleeve to the interior of the sleeve, and the interior of saidsleeve serving to conduct the scavenge air on its way to said frontworking chamber.

6- Re ip cating parts for use in a double acting two stroke cycleinternal combustion engine comprising a working piston, a first valvepiston and a second valve piston, said valve pistons being smaller indiameter than said working piston, said valve pistons being fastened oneon each end of said working piston so as to form a reciprocating pistonassembly, said valve pistons and said working piston being integrallycast together, said piston assembly having a hollow interior, said twovalve pistons having open ends so as to provide support for a core whendoing the casting job, a piston rod passing through said hollowinterior, said piston rod and its appurtenances serving to close saidopen ends of the valve pistons, said piston rod serving to clamp saidpiston assembly in compression, said piston assembly being subjected tocompression loads due to the clamping action of said piston rod and alsodue to combustion gas pressure forces acting alternately against eachannular face of the working piston, said working piston having radiallydirected ribs located within its hollow interior, and said ribs servingto transmit said compression loads along the piston assembly so as toprevent structural failure of the working piston, said piston rod beinghollow along at least part of its length, said hollow piston rod servingto conduct liquid coolant into the hollow interior of said pistonassembly, and aperture means for conducting the liquid coolant back outof the piston assembly, said aperture means being in communication withambient air whereby said hollow interior of the piston assembly isallowed to fill partly with liquid coolant and partly with air so as toobtain a shaking action of the liquid coolant inside the pistonassembly, and said shaking action serving to provide good distributionof the liquid coolant inside the piston assembly.

7. Reciprocating parts for use in a double acting two stroke cycleinternal combustion engine comprising a working piston, two valvepistons, said valve pistons being smaller in diameter than said workingpiston, said valve pistons being fastened one on each end of saidworking piston so as to form a reciprocating piston assembly, saidpiston assembly having a hollow interior, a piston rod passing throughsaid hollow interior, said piston rod being attached to said pistonassembly, said piston rod being hollow along at least part of itslength, a tube located inside the hollow piston rod, said tube and thehollow portion of said piston rod serving to conduct liquid coolant toand from said piston assembly, said hollow piston rod having holespassing through its wall and opening into the hollow interior of thepiston assembly for the flow of said liquid coolant, the hollow interiorof said piston assembly being filled partly with liquid coolant andpartly with air during operation of said engine so as to obtain ashaking action of the liquid coolant inside the piston assembly, andsaid shaking action serving to provide good distribution of the liquidcoolant inside the piston assembly.

8. The combination recited in claim 7 wherein at least one of said holesin the piston rod serves as an orifice for controlling the rate of flowof liquid coolant leaving the piston assembly so as to maintain aproportion of both liquid coolant and air inside the hollow interior ofthe piston assembly.

9. In a double acting two stroke cycle internal combustion engine, thecombination of a crankcase, a crosshead guide fastened to saidcrankcase, a working cylinder, a front cylinder head and a back cylinderhead fastened to said working cylinder, said cylinder heads havingreduced diameter bores therein, said working cylinder and said cylinderheads being fastened to said crosshead guide, a crankshaft rotatablymounted in said crankcase, a crosshead reciprocable in said crossheadguide, a connecting rod interconnecting said crosshead and saidcrankshaft for respective reciprocating and rotary motion, a doubleacting working piston reciprocable in said working cylinder, a frontvalve piston and a back valve piston attached to said working piston soas to form a reciprocating piston assembly, said valve pistons beingreciprocable in the bores of their respective cylinder heads, a separatescavenge pump for supplying scavenge air, said cylinder heads havinginlet ports interrupting the walls of said bores therein, each valvepiston being adapted to uncover a respective said inlet port so as toadmit scavenge air into the interior of said working cylinder, eachvalve piston having a groove in its outer cylindrical surface, anexpanding type seal ring mounted in each of said grooves, said workingcylinder having exhaust ports controlled by said working piston, saidworking cylinder having uniflow type scavenging operations exhaustingthrough said exhaust ports, a piston rod interconnecting said pistonassembly and said crosshead for reciprocative motion, said piston rodbeing smaller in cross section than the diameter of said front valvepiston, swirl vanes surrounding asid piston rod and reciprocabletherewith, and said swir-l vanes serving to impart a rotational velocityto the scavenge air prior to passage of the air through said front inletports.

References Cited UNITED STATES PATENTS 745,704 12/ 1903 Westinghouse123-65 1,157,347 10/1915 Ver Planck 123-4135 1,175,017 3/1916 Seymour123-65 1,201,731 10/1916 Hinkley 123-52 1,900,133 3/ 1933 Schaeffers123-65 2,034,585 3/1936 Lipetz 123-61 FOREIGN PATENTS 413,616 5/1910France.

265,097 10/1913 Germany.

132,121 9/1919 Great Britain.

366,129 2/ 1932 Great Britain.

CARLTON R. CROYLE, Primary Examiner. WENDELL E. BURNS, Examiner.

6. RECIPROCATING PARTS FOR USE IN A DOUBLE ACTING TWO STROKE CYCLEINTERNAL COMBUSTION ENGINE COMPRISING A WORKING PISTON, A FIRST VALVEPISTON AND A SECOND VALVE PISTON, SAID VALVE PISTONS BEING SMALLER INDIAMETER THAN SAID WORKING PISTON, SAID VALVE PISTONS BEING FASTENED ONEON EACH END OF SAID WORKING PISTON SO AS TO FORM A RECIPROCATING PISTONASSEMBLY, SAID VALVE PISTON AND SAID WORKING PISTON BEING INTEGRALLYCAST TOGETHER, SAID PISTON ASSEMBLY HAVING A HOLLOW INTERIOR, SAID TWOVALVE PISTONS HAVING OPEN ENDS SO AS TO PROVIDE SUPPORT FOR A CORE WHENDOING THE CASTING JOB, A PISTON ROD PASSING THROUGH SAID HOLLOWINTERIOR, SAID PISTON ROD AND PASSING THROUGH SAID SERVING TO CLOSE SAIDOPEN ENDS OF THE VALVE PISTONS, SAID PISTON ROD SERVING TO CLAMP SAIDPISTON ASSEMBLY IN COMPRESSION, SAID PISTON ASSEMBLY BEING SUBJECTGED TOCOMPRESSION LOADS DUE TO THE CLAMPING ACTION OF SAID PISTON ROD AND ALSODUE TO COMBUSTION GAS PRESSURE FORCES ACTING ALTERNATELY AGAINST EACHANNULAR FACE OF THE WORKING PISTON, SAID WORKING PISTON HAVING RADIALLYDIRECTED RIBS LOCATED WITHIN ITS HOLLOW INTERIOR, AND SAID RIBS SERVINGTO TRANSMIT SAID COMPRESSION LOADS ALONG THE PISTON ASSEMBLY SO AS TOPREVENT STRUCTURAL FAILURE OF THE WORKING PISTON, SAID PISTON ROD BEINGHOLLOW ALONG AT LEAST PART OF ITS LENGTH, SAID HOLLOW PISTON ROD SERVINGTO CONDUCT